Ebola: facing a new transboundary animal disease?

Ebola viruses are zoonotic pathogens with the potential of causing severe viral hemorrhagic fever in humans and nonhuman primates. Bats have been identified as a reservoir for Ebola viruses but it remains unclear if transmission to an end host involves intermediate hosts. Recently, one of the Ebola species has been found in Philippine pigs raising concerns regarding animal health and food safety. Diagnostics have so far focused on human application, but enhanced pig surveillance and diagnostics, particularly in Asia, for Ebola virus infections seem to be needed to establish reasonable guidelines for public and animal health and food safety. Livestock vaccination against Ebola seems currently not justified but proper preparedness may include experimental vaccine approaches.

UK B.1.1.7 variant exhibits increased respiratory replication and shedding in nonhuman primates.

The continuing emergence of SARS-CoV-2 variants calls for regular assessment to identify differences in viral replication, shedding and associated disease. In this study, African green monkeys were infected intranasally with either a contemporary D614G or the UK B.1.1.7 variant. Both variants caused mild respiratory disease with no significant differences in clinical presentation. Significantly higher levels of viral RNA and infectious virus were found in upper and lower respiratory tract samples and tissues from B.1.1.7 infected animals. Interestingly, D614G infected animals showed significantly higher levels of viral RNA and infectious virus in rectal swabs and gastrointestinal tract tissues. Our results indicate that B.1.1.7 infection in African green monkeys is associated with increased respiratory replication and shedding but no disease enhancement similar to human B.1.1.7 cases. ONE-SENTENCE SUMMARY: UK B.1.1.7 infection of African green monkeys exhibits increased respiratory replication and shedding but no disease enhancement.

Microbial persistence. II. Characteristics of the sterile state of tubercle bacilli.

The capability of tubercle bacilli to assume a long continued sterile state in the tissues when exposed to pyrazinamide and isoniazid is a highly specific drug-microbe phenomenon in which host participation is not critical. Although it is the pyrazinamide that possesses the sterilizing type of action, the role of the isoniazid is specific and essential. The isoniazid serves to convert a phenomenon that occurs irregularly with pyrazinamide alone into one that occurs with a high degree of uniformity. The observations suggest a competition between isoniazid and the pyrazinamide (or its parent nicotinamide) for a site or entrance in or on the tubercle bacilli and for sterilization, the isoniazid apparently must reach the site first. The rare failures to attain complete sterilization, appear to depend on the emergence of pyrazinamide-resistance which prevents the necessary dependent action of the two drugs. Populations already in the sterile state are nevertheless subject to a continued drug influence. Whether this represents a direct action on the sterile bacilli or an indirect effect produced by making the environment hostile to microbial revival, cannot be determined from the present observations.

Microbial persistence. I. The capacity of tubercle bacilli to survive sterilization in mouse tissues.

A previously reported form of microbial persistence whereby large populations of tubercle bacilli can be made to "vanish" uniformly from the tissues of mice has been shown to occur generally throughout each group of animals subjected to the experimental procedure; it does not reflect the eradication of the bacilli in the majority of animals with their persistence and ultimate revival in only a minority. The one demonstrable alteration of the tubercle bacilli while "vanished" is that they are sterile. Thus, they are undetectable by cell-free culture, tissue culture, and blind animal passage, i.e. by any method based on microbial multiplication. Whether they have also undergone alteration in morphology and persist in some unconventional form cannot be stated. Acid-fast forms similar to tubercle bacilli can be detected in small numbers by intensified microscopic search of tissue homogenates but the relationship of these forms to the sterile bacilli that ultimately revive is unclear. Thus, the persisting tubercle bacilli are more correctly designated as being in a "sterile state" than one of true latency. The uniform induction of the sterile state is a specific phenomenon requiring the participation of both the nicotinamide derivative, pyrazinamide, and isoniazid. Once assumed, this sterile state is relatively stable and the time required for revival of the tubercle bacilli in the spleens in one-half the animals is seven months. This process can be speeded up by the administration of large doses of cortisone in the third or fourth month after sterilization but revival is not significantly affected by the administration of cortisone earlier.

The Ebola virus ribonucleoprotein complex: a novel VP30-L interaction identified.

The ribonucleoprotein (RNP) complex of Ebola virus (EBOV) is known to be a multiprotein/RNA structure, however, knowledge is rather limited regarding the actual protein-protein interactions involved in its formation. Here we show that singularly expressed VP35 and VP30 are present throughout the cytoplasm, while NP forms prominent cytoplasmic inclusions and L forms smaller perinuclear inclusions. We could demonstrate the existence of NP-VP35, NP-VP30 and VP35-L interactions, similar to those described for Marburg virus (MARV) based on the redistribution of protein partners into NP and L inclusion bodies. Significantly, a novel VP30-L interaction was also identified and found to form as part of an NP-VP30-L bridge structure, similar to that formed by VP35. The identification of these interactions allows a preliminary model of the EBOV RNP complex structure to be proposed, and may provide insight into filovirus transcriptional regulation.

Virology. Mutation rate and genotype variation of Ebola virus from Mali case sequences.

The occurrence of Ebola virus (EBOV) in West Africa during 2013-2015 is unprecedented. Early reports suggested that in this outbreak EBOV is mutating twice as fast as previously observed, which indicates the potential for changes in transmissibility and virulence and could render current molecular diagnostics and countermeasures ineffective. We have determined additional full-length sequences from two clusters of imported EBOV infections into Mali, and we show that the nucleotide substitution rate (9.6 × 10(-4) substitutions per site per year) is consistent with rates observed in Central African outbreaks. In addition, overall variation among all genotypes observed remains low. Thus, our data indicate that EBOV is not undergoing rapid evolution in humans during the current outbreak. This finding has important implications for outbreak response and public health decisions and should alleviate several previously raised concerns.

Complete genome sequences of three ebola virus isolates from the 2014 outbreak in west Africa.

Here, we report the complete genome sequences, including the genome termini, of three Ebola virus isolates (species Zaire ebolavirus) originating from Guinea that are now being widely used in laboratories in North America for research regarding West African Ebola viruses.

Inhibition of Myb-dependent gene expression by the sesquiterpene lactone mexicanin-I.

The c-myb proto-oncogene encodes a transcription factor that is highly expressed in the progenitor cells of the hematopoietic system, where it regulates the expression of genes important for lineage determination, cell proliferation and differentiation. There is strong evidence that deregulation of c-myb expression is involved in the development of human tumors, particularly of certain types of leukemia, and breast and colon cancer. The c-Myb protein is therefore an interesting therapeutic target. Here, we have investigated the potential of natural sesquiterpene lactones (STLs), a class of compounds that are active constituents of a variety of medicinal plants, to suppress Myb-dependent gene expression. We have developed a test system that allows screening of compounds for their ability to interfere with the activation of Myb target genes. Using this assay system, we have identified the STL mexicanin-I as the first cell-permeable, low-molecular-weight inhibitor of Myb-induced gene expression.

Binding of the CryIVD Toxin of Bacillus thuringiensis subsp. israelensis to Larval Dipteran Midgut Proteins.

Ligand-blotting experiments on dipteran brush border membrane vesicles (BBMVs) showed binding of CryIVD toxin of Bacillus thuringiensis subsp. israelensis to proteins of 148 kDa in Anopheles stephensi and of 78 kDa in Tipula oleracea, both species being susceptible to CryIVD. Binding of CryIVD with BBMVs of A. stephensi resulted in a stronger signal than with BBMVs of T. oleracea. Likewise, larvae of A. stephensi are 10,000-fold more susceptible to the CryIVD toxin than are larvae of T. oleracea. Binding was also found with six proteins ranging in size from 48 to 110 kDa in BBMVs from the lepidopteran species Manduca sexta, but CryIVD was not toxic for M. sexta larvae. No binding of trypsinated CryIVD to BBMV proteins was observed. With the lepidopteran-specific toxin CryIA(b), no binding to dipteran BBMVs was found. Binding of CryIA(b) to nine different BBMV proteins ranging in size from 71 to 240 kDa was observed in M. sexta. The major binding signal was observed with a protein of 240 kDa for CryIA(b).